feat(wallet): special-case descriptor for single-guardian instances

[elsirion]

Using p2wpkh is more efficient than a 1-of-1 multisig

[codecov]

Codecov Report

Attention: 19 lines in your changes are missing coverage. Please review.

Comparison is base (f6f368d) 57.48% compared to head (5b9c5ac) 57.51%.
Report is 3 commits behind head on master.

Files	Patch %	Lines
devimint/src/main.rs	0.00%	10 Missing ⚠️
modules/fedimint-wallet-common/src/config.rs	30.76%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3821      +/-   ##
==========================================
+ Coverage   57.48%   57.51%   +0.03%     
==========================================
  Files         193      193              
  Lines       42185    42209      +24     
==========================================
+ Hits        24248    24275      +27     
+ Misses      17937    17934       -3     

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[benthecarman]

Could also do taproot

Are no changes needed for the spending? Does miniscript handle it all here?

[elsirion]

Are no changes needed for the spending? Does miniscript handle it all here?

Yes, the beauty of descriptors and generic satisfiers! I tested it and it works, I didn't expect any problems, it's only getting easier for the satisfier.

Could also do taproot

1. Will limit who can send to these addresses
2. It, and thus also implementations like in rust-miniscript, are less lindy. I read and worked with the non-taproot part of rust-miniscript in the past, not at all the TR part of it, so I'm less confident in that.

[dpc]

Is there a single test anywhere that makes sure this works?

[elsirion]

I added devimint CLI tests for single guardian federations (FYI @joschisan), should have done that sooner. I think it won't slow down CI much since all these tests can run in parallel (they don't take a lot of CPU once compiling is done).

[justinmoon]

LGTM

[justinmoon]

Does recovery tool need to be updated to support this?

[bradleystachurski]

Does recovery tool need to be updated to support this?

Capturing what we discussed in the dev call: We don't need to update the recovery tool to support, however it doesn't hurt to add a test case.

#3916